Chevy Caprice Nitrous Kit - Killer Whale, Part 3

Police Action--Adding A Zex Nitrous System Catapults Our Cop Car Into The Mid-13s

Want to put some beef into your pig? Then add a Zex nitrous system to your car and get up to 125 additional horsepower. We did, and as a result, we now have a Caprice that runs 13.50s.

It's been three months since we took delivery of the Killer Whale, and we're just smitten with its performance, all-around capability, and off-the-charts fun factor. Not only has it proven to be stone reliable, but it's also incredibly comfortable for the daily grind and has shown its merits both on the dragstrip and on the streets. Better yet, we've averaged about 20 mpg in combined city and highway driving, proving that LT1 performance comes with little sacrifice at the pump. With well over 115,000 miles on the clock, those 5.7 liters of American willpower are still firin' on all eight and have readily accepted all the mods we've thrown at it without a single hiccup.

Thanks to the Level 10 transmission and torque converter, as well as the slew of new and used bolt-ons, we've whittled our elapsed times from a baseline of 15.251 at 91.11 to a rather impressive 14.405 at 92.81 mph. But at this point, we're pretty much done with the bolt-on mods, and our quest for quicker quarter-mile times has redirected our performance focus toward more substantial modifications. It's a natural progression, really. Question is, which way do we go?

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Included in the LT1-specific nitrous kit by Zex (PN 82018) is a self-contained management unit that houses all the solenoids, electronics, and plumbing systems; a 10-pound aluminum bottle powdercoated in Zex's signature gloss purple; an inline fuel pump; and all the wiring and hardware necessary for a complete installation. New spark plugs are recommended with any nitrous installation, so we went with Zex's own line of Power Tune performance spark plugs (PN 82070-8) for a more assured spark.

Good Cop, Bad CopSo there we were, racking that gray matter for the best way to step up our game to increase power. After weighing our options, we decided that a power adder would be a good way to start, as opposed to a full-on naturally aspirated engine buildup. We then had to choose which power adder, and the choices only complicated things some more (in case you weren't aware, our brains aren't exactly the swiftest of machines).

At first, we looked at supercharging, but the subsequent commitment to precise PCM tuning and the added weight was unappealing in the long run. This would also hold true for a turbocharger system that would throw increased underhood temps into the equation. In the end, nitrous oxide made the most sense because of its simplicity and affordability. There is nothing as effective, dollar for dollar, as a good nitrous system.

When looking for a nitrous system, there will be many questions surrounding the topic. Do you want a dry or wet system? How much power do you want to add? How much time do you want to spend on installation? Once you get your answers, you'll have a clearer picture as to what you want so you can make a more educated choice. For our application, we found the Zex system to our liking the most. Let us explain why.

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First up, we found a spot for the nitrous nozzle that was close to the throttle body. We then drilled a hole into the air inlet tube and mounted the brass fitting that the nozzle itself threads into. The dimple in the hex part lets you know which direction the nozzle will discharge while you're tightening it down.

Although there are no less than seven nitrous oxide companies out there offering systems for fuel-injected V-8s, we turned our short attention spans to the manufacturers of dry kits. By injecting the nitrous oxide directly into the air induction system and allowing the existing fuel injectors to provide the requisite additional fuel, this clean and effective setup reduces the chances of massive backfires. On an older car like ours, using a wet nitrous system that injects both gasoline and nitrous simultaneously into the intake manifold can prove to be dicey. This is because all the fuel being injected can sit in the manifold and cylinder head's ports and get absorbed into the oil sludge and carbon buildup like a sponge, making it a bomb in the event of a slight backfire. All that fuel wants to combust, and it will rip apart expensive hard parts in the process. Therefore, a dry kit is the safer, more preferred choice for our Killer Whale.

There are only a few LT1-specific dry manifold nitrous kits on the market, but by far the easiest one to install and maintain is produced by Zex. It offers a kit that's adjustable from 75 to 125 additional horsepower. Some people may get greedy and feel the need for more power and shun kits that are maxed out at 125, but those who are in the know understand that with a stock engine, this is the safe mechanical limit. Besides, we'd rather keep our rods and pistons inside our block rather than out of it. And yes, because it's designed for LT1 GM cars, it comes ready to install specifically for our application.

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Next up, it's time to install the nitrous jet and the braided line. For a 125-shot, you're going to slide in a 52 jet.

The total installation took the better part of an afternoon to complete-about 5.5 hours-with basic tools and an above-average technician spinning the wrenches. This included the installation of the inline fuel pump that was supplied with the kit to ensure a steady head of liquefied lizards at the fuel rail. Luckily, our Caprice has a lot of space by the fuel tank area to make installation easy.

Because the Zex system has the solenoids, wiring, and other major connections all assembled and housed inside a purple-anodized management unit, installation is greatly simplified compared to other kits that we have installed. We simply mounted the management unit to the driver-side inner fender and began hooking up the system's uncomplicated connections. Two hoses go to the fuel pressure regulator's signal line and allow normal operation when the nitrous system is switched off. When the nitrous is armed and activated, a regulated amount of high-pressure nitrous oxide gas pressurizes the fuel pressure regulator's diaphragm and spikes the fuel pressure to about 85 psig, subsequently increasing the flow rate of the fuel injectors by about 50 percent. This is how additional fuel is added to each cylinder to complement the nitrous oxide.

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Now that we have the nozzle installed, we connected the line to the management unit and then mounted it to the steel inner fender. We kept it accessible so that we could easily reach it down the road should we need to make any adjustments.

On the other side of the management unit, we ran the braided stainless steel nozzle line to the nozzle itself that was mounted in the air tube just upstream of the throttle body. Zex recommends installing the nitrous nozzle as close to the throttle body as possible for enhanced response time, so we did as we were told. We then hooked up the 16-foot nitrous feed line to the back of the car and into the trunk area, where we mounted the 10-pound aluminum bottle with the supplied brackets.

Because the Zex management unit has a microprocessor built in that can detect WOT based on a five-volt signal from the TPS (throttle position sensor), there's no need to mount a traditional on-off microswitch on the throttle linkage. All we had to do was splice into the output signal wire coming out of the TPS as it goes into the PCM (Powertrain Control Module) and program the Zex controller to detect the WOT voltage point as the instructions explained.

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Here, the two lines that splice into the fuel pressure regulator's manifold pressure reference hose are clearly labeled. We simply used the supplied fittings and hose to make the connections. By the way, the fuel jet here is a 73, and it's mounted in an inline brass fitting.

While we were under the hood, we decided to pull out the stock spark plugs and install a fresh set of Zex units. These Power Tune spark plugs are designed for LT1 applications and performance use with or without nitrous oxide. When not subjected to the power adder's increased cylinder pressures, they also provide a cleaner, more efficient spark thanks to a tip design with multiple electrodes that transfers more spark energy across the gap and takes heat away more quickly. Pretty neat stuff.

Gettin' off like O.J.With our Zex system installed and our drag radials mounted, we headed back to Old Bridge Township Raceway Park in New Jersey to see what kind of gain we'd be rewarded with on the dragstrip. The car was seriously strong on the street when armed with nitrous, and we knew that getting a good number wasn't going to be all that hard. On the line, we stalled up the converter a little (we have no tachometer to tell you exactly where, but it sounds like mmmmm) and flat-punched it with the nitrous system locked and loaded. Incredibly, the car torqued over and spun the tires, pointing the car toward the wall. We quickly aborted the run and decided to let the track get a little warmer before we hit it again. The anticipation was high, and we let the car cool down for another run.

On the next pass, we did a lengthy burnout, putting plenty of heat into the Nitto drag radials, which were inflated to 17 pounds. On the line, we again stalled up the converter, and once the green light dropped, we flat-punched the car and it shot off the line with a rather strong 1.78 short time. With the car running like a champ all the way down the track, we were wowed by the 13.522 at 98.70 mph that was printed on the timeslip in our hands. We improved our e.t. by almost nine tenths (0.883 seconds, to be exact) and picked up 5.89 mph from our previous best of 14.405 at 92.81 mph without nitrous. In the 60-foot time alone, we went from a 2.051 to a 1.780.

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Our Caprice had a large black plastic sheathing that was probably once occupied by numerous power wires for sirens and lights. It now serves as a safe place for us to route our nitrous feed line. Then we simply followed the wiring harness to the trunk area and secured everything down with the factory wiring mounts.

Just for shifts and giggles, we drove our Killer Whale from the track right onto the Dynojet 248c over at Crazy Horse Racing in nearby South Amboy, New Jersey. Once the dyno rollers were stopped, we were pleased to find 346 horsepower and 407.3 lb-ft of torque at the wheels from our nitrous-enhanced LT1.

This sounded a little low to us on both the horsepower and torque, considering that we used the 125-horse jets. The torque question was easily answered because we did not activate the nitrous until 3,500 rpm, which was well past the torque peak that normally occurs at 2,900 rpm. To compare apples to apples, we should look at the torque at the same engine speed at, say, 3,800 rpm. This was where torque was up by 87 lb-ft. But it still didn't explain why we weren't making much power. A quick peek at a borrowed nitrous pressure gauge revealed that we had only 750 psig of nitrous pressure, which was well below the minimum recommended 900-1,000 psig. This explained the power difference between the advertised numbers and what we got on the track and dyno. It also reminded us why no nitrous kit should be installed without a bottle warmer and gauge. When we get more time, we'll go back with a full head of nitrous and get you a better number. But the results from this exercise are certainly incredible.

In the end, we've proven that nitrous is indeed an irresistible power adder. Its simple installation does not require any special tools, trick computer tuning, or big-dollar support items such as massive fuel pumps, injectors, and ignition upgrades. Installed at home with just a few tools, we were able to drop our Caprice solidly into the mid-13s.

When bolt-ons aren't no longer appealing, you move onto the engine and that is exactly what they did with the 1992 Chevy Caprice by installing Edelbrock's Performer LT1 aluminum cylinder heads, high lift valvesprings, hydraulic roller camshafts, and CNC port matched runners. » Read More